Round Quick-Acting Watertight Hatch Cover | CB/T 3842 Type A

Product Overview

The CB/T 3842-2000 Type A quick-acting watertight hatch cover is a round marine access closure for vessel positions where a watertight boundary and rapid local opening are required. The standard arrangement combines a circular steel cover, coaming, sealing packing, central handwheel-operated clamping device, and spring balancing mechanism. The Type A size series provides clear openings from 600 to 800 mm and is specified for a design pressure of 0.2 MPa.

The handwheel can be operated from either side of the closure, allowing the locking mechanism to be released or tightened without individually operating every securing point. The spring balancing arrangement assists the movement of the heavy cover, while the gasket and seating surface provide the sealing interface. Selection should be based on the approved access opening, installation orientation, coaming height, surrounding deck or bulkhead reinforcement, operating clearance, gasket compound, coating system, test requirement, and class approval scope. Higher-pressure, larger-size, or gas-tight versions require separate engineering confirmation and approval.

Quick Specifications

• Product type: Round quick-acting watertight small hatch cover → provides a rapidly operated access closure at a watertight boundary.
• Standard and type: CB/T 3842-2000 Type A → round configuration; the related Type B configuration is square and should not be mixed with this page.
• Clear opening range: 600 / 650 / 700 / 750 / 800 mm → select according to required personnel access, approved cut-out, and vessel arrangement drawing.
• Design pressure: 0.2 MPa → pressure basis stated for the standard Type A range; project location and boundary rating must still be approved by the vessel designer and class.
• Hydraulic test basis: 1.5 × design pressure = 0.3 MPa → test duration, acceptance criteria, and witnessing scope should be stated in the order.
• Operating arrangement: Central clamping device operated by handwheel from either side → supports quick release and re-tightening while maintaining access from both spaces.
• Opening assistance: Spring balancing mechanism → reduces operating effort for covers weighing approximately 245-328 kg; hinge condition and spring adjustment remain maintenance items.
• Construction options: Mild steel or stainless steel with Neoprene / NBR / Hi-NBR packing → exact grades, gasket compound, finish, and certificate scope must be confirmed before production.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm CB/T 3842-2000 Type A round configuration and select clear opening D600-D800 according to the approved access and arrangement drawing.

Step 2: Confirm the required boundary performance: standard 0.2 MPa watertight duty, test pressure and duration, or a separately engineered higher-pressure / gas-tight requirement subject to approval.

Step 3: Provide the installation position and orientation, deck or bulkhead cut-out, coaming height, surrounding reinforcement, weld detail, opening direction, and available cover-swing clearance.

Step 4: Confirm operation and sealing details: handwheel access from both sides, central clamping / dog-wedge arrangement, spring balancing direction, gasket profile, gasket compound, and replacement requirement.

Step 5: Confirm material and surface treatment: mild steel or stainless steel, Sa 2.5 blasting plus epoxy shop primer, galvanized or polished finish where technically suitable, and final vessel coating system.

Step 6: State quantity, vessel type, class society, material and test certificate scope, witness inspection requirement, delivery destination, required delivery time, and reference drawing or photos.

Structure

Round cover plate | Circular coaming | Replaceable sealing packing | Central handwheel-operated clamping device | Dog / wedge tightening points | Spring balancing hinge | Seating and compression surface | Welded ship-structure interface | Interior and exterior operating access

Sealing, Operation & Installation Advantages

• The central clamping device coordinates the securing points through one handwheel operation, reducing the opening and closing sequence compared with individually operated dogs.
• Spring balancing assists movement of the cover but does not remove its mass. Hinge alignment, spring preload, stops, and safe hold-open arrangements should be checked during installation and maintenance.
• Watertight performance depends on controlled gasket compression around the full circular seat. Cover flatness, coaming roundness, seating-surface finish, clamp adjustment, and gasket condition are therefore key inspection points.
• The 200 mm standard-reference coaming height helps define the installation envelope. A higher coaming can be produced only after checking plate thickness, stiffness, access ergonomics, weld distortion, and project approval requirements.
• Fabrication control should limit distortion of the cover and coaming so that the clamp linkage can apply even compression. Threads, pins, wedges, hinge points, and gasket-contact areas should remain accessible for inspection and lubrication.
• Mild-steel units normally require blasting, shop primer, and final vessel coating. Stainless-steel versions require grade confirmation, compatible fasteners, and controlled surface finishing; coating or galvanizing must not impair threads, seats, gasket grooves, or moving parts.

Custom Attributes

• Standard: CB/T 3842-2000 → reference for Type A classification, size series, structure, test, inspection, marking, packing, and transport requirements.
• Type: A, round → use where the approved vessel drawing specifies a circular access opening; Type B is the square alternative.
• Clear Opening: D600-D800 → determines access size and the related D1 / D2 / D3 installation dimensions.
• Design Pressure: 0.2 MPa → standard pressure basis for this page; actual installation boundary must be accepted by the vessel designer and class.
• Hydraulic Test: 0.3 MPa based on 1.5 × design pressure → duration, leakage criterion, permanent-deformation criterion, and witness requirement to be confirmed.
• Operation: Handwheel operable from both sides → provides quick local release and tightening through the central clamping mechanism.
• Seal Material: Neoprene / NBR / Hi-NBR → select according to temperature, oil exposure, ageing, compression set, and project specification.
• Material: Mild steel or stainless steel → exact plate, spindle, dog, pin, spring, and fastener grades are to be confirmed.
• Coaming Height: 200 mm minimum standard reference → alternative height requires approved dimensional and structural confirmation.
• Special Duty: Higher pressure, larger size, or gas-tight version → available only as a project-specific design subject to testing and class approval.

How It Works

Turn the handwheel from either side → Central clamping device retracts the dog / wedge points → Spring balancing assists the cover to open → Access opening is used → Cover is lowered onto the circular sealing seat → Handwheel drives the locking points into the tightened position → Gasket is compressed around the full circumference → Closure condition and watertightness are checked

Applications

Watertight access openings on ships | Weather-exposed or internal watertight boundaries according to approved arrangement | Cargo vessels | Tankers | Tugboats | Workboats | Service vessels | Newbuilding and replacement projects

Certifications & Advantages

Certificates and inspection can be arranged according to project requirement, material traceability, hydraulic test scope, witness plan, and classification society approval procedure.

Certification: CCS, NK, BV, ABS, DNV, LR, KR, IRS, RS, RINA, CRS, Makers Test Certificate.

Drawing & Photos

FAQ

Q1: How should the correct Type A hatch-cover size and coaming height be selected?

A1: Select D600-D800 from the approved access requirement and verify opening size D1, coaming inside diameter D2, cover outside diameter D3, installation orientation, and structural opening. The standard-reference H = 200 mm is a minimum value in the available standard preview; a different height should be shown on the approved drawing.

Q2: Is the standard Type A hatch cover automatically suitable for gas-tight or higher-pressure service?

A2: No. This page is based on 0.2 MPa watertight duty. Gas-tight service, a pressure above 0.2 MPa, or a size outside D600-D800 requires separate sealing design, strength review, test criteria, and class approval before quotation or production.

Q3: What information is required before quotation?

A3: Provide standard and type, clear opening, coaming height, installation position and orientation, surrounding structure drawing, material, gasket compound, surface treatment, design and test pressure, quantity, certificate scope, class society, destination, and required delivery time.